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Rationally Speaking is a blog maintained by Prof. Massimo Pigliucci, a philosopher at the City University of New York. The blog reflects the Enlightenment figure Marquis de Condorcet's idea of what a public intellectual (yes, we know, that's such a bad word) ought to be: someone who devotes himself to "the tracking down of prejudices in the hiding places where priests, the schools, the government, and all long-established institutions had gathered and protected them." You're welcome. Please notice that the contents of this blog can be reprinted under the standard Creative Commons license.

Wednesday, December 30, 2009

From the APA: Darwinism and mind

[Warning to the general reader: this is going to be pretty technical, especially the first part...]

This is a symposium organized by Robert Brandon (Duke), featuring Karen Neander (also from Duke) and John Dupré (Exeter, England). Neander talks about functional explanations in biology in terms of “biosemantics” (an approach that attempts to explain intentionality in biological terms, particularly by invoking the process of natural selection).

Ernst Mayr famously distinguished two types of explanations in biology, proximate and ultimate. The first is a type of functional explanation (the heart has the function of pumping blood), the second is an evolutionary or teleological one (the heart evolved from simpler structures to further the survival and reproduction of organisms belonging to certain lineages). Neander criticizes what she sees as the standard view of these types of explanation, which says that only functional explanations are needed in physiology, no need to bring in teleological explanations because causation in physiology is proximal (this was in fact Mayr’s position).

Neander maintains that physiology clearly employs a normative definition of biological function, every time people make a distinction between “normal” and “abnormal” physiology (normal with respect to what standard?). The claim would then be that one cannot get to a normative function except through a teleological (evolutionary) explanation. Neander proceeded for quite some time after this, but the point seems to me rather obvious: physiological functions cannot be fully explained without evolution. In a vague — yet potentially misleading — sense then “intentionality” gets extended to any biological structure that has been selected (without true “intention”) to perform a given function.

Dupré in the Q&A defended the “standard” view, suggesting that a physiologist really is going to be distracted by asking evolutionary (“why”) questions when in fact he wishes to understand how biological structures work. As for the normative part, Dupré proposes that physiology does need a theory of normal and abnormal function, but that it does not need evolution to arrive at one. (I think on this one I tend to agree with Dupré.)

Also in the Q&A, Peter Godfrey-Smith pointed out a case in biology where normative functionality is out of place: community and ecosystem ecology. Although ecologists often talk about “ecosystem functions,” “keystone predators,” etc., they don’t (or should not) mean that things are “supposed” to work that way. But here Neander correctly points out that the difference is that in physiology, but not those cases in ecology, function is a result of natural selection, and therefore teleological (originated for a purpose).

Dupré’s talk is on “post-genomic Darwinism and human nature.” This ought to be interesting... [Great! He’s the first speaker I’ve seen here who actually uses a computer presentation!]

John claims that the work of evolutionary theory (which he somewhat incorrectly refers to as neo-Darwinism, instead of the Modern Synthesis) is far from over, contrary to what many biologists (not including yours truly) seem to think. He takes issue with several of the “neo-Darwinian” tenets, including that natural selection is the main cause of adaptation, that variation is originated endogenously, that genes are the targets of selection, and that evolutionary change always occurs gradually.

Dupré’s focus is on the picture/metaphor of the tree of life, non-genetic causes of adaptation (like phenotypic plasticity), and non-genetic (i.e., epigenetic) inheritance.

In terms of the tree of life, it is becoming increasingly clear that horizontal transfer of genes during evolution has played an unexpectedly large role, changing the metaphor of common descent from that of a tree to that of a very intricate web. For instance, there definitely is no unique tree for prokaryotes, given the high level of horizontal gene transfer in microbes. Even among eukaryotes, we have evidence of more hybridization than previously thought, depending on the particular group (especially in plants, I’d say). And of course let’s not forget viral-enabled horizontal transfer (just think that 10% of the human genome is made of fragments from former retroviruses). Finally, there is endosymbiosis as an occasional but important evolutionary mechanism. (Though, I never bought Lynn Margulis’ argument that this somehow undermines “Darwinism.”)

Dupré suggests that the evolutionary literature over-emphasizes competition and does not take seriously that organisms often form cooperative wholes in order to survive. The “neo-Darwinian” account of cooperation is limited to Hamilton-style kin selection, which seems inadequate to explain the full spectrum of cooperation among living organisms. Consider for instance Argentine ant “supercolonies” marching throughout Europe, a situation where individual colonies of ants coordinate over thousands of miles through connections among billions of individuals. The next example is of human super colonies, i.e. armies made possible by cultural evolution. In general, though, the best examples of cooperation are actually found among microbes. This is important because arguably most of earth’s biochemistry is made possible by different combinations of microbial pathways. As far as humans are concerned, 90% of cells in the human body are symbiotic microbes, which means that 99% of genes inside a human being actually reside in microbes.

John then moved to Lamarckism, a notoriously bad word in biological lingo, though he was careful in pointing out that he does not employ the term in the historical sense (then why employ it at all, just to piss off a large number of biologists?). He is actually talking about non-genetic inheritance of various types, from epigenetic to cultural, all of which can be understood in the context of what philosophers call developmental systems theory.

Dupré finally got to human nature, in this case arguing that evolution actually tells us very little about what we are like. This is in part because we don’t know enough about evolutionary processes to use the theory predictively (is that even possible, I wonder?), because naive adaptationism based on the idea of optimizing selection is simply false, and because humans do not have (enough) close relatives for meaningful phylogenetic comparative analyses. No disagreement here, as I’ve argued in a variety of places myself.

The alternative view John puts forth is that we should take much more seriously cultural evolution (and/or its interaction with biological evolutionary mechanisms), which explains how humans became humans with comparatively little input from standard genetic evolutionary theory.

6 comments:

The alternative view John puts forth is that we should take much more seriously cultural evolution (and/or its interaction with biological evolutionary mechanisms), which explains how humans became humans with comparatively little input from standard genetic evolutionary theory.

Try, just TRY convincing most people of this. You can't do it. They are emotionally wedded to the idea that natural selection and genetics can tell us interesting and important facts about "human nature".

The idea is basically a disease in our intellectual culture, one which has taken a firm hold in pop-psychology, pop-sociology, etc., and which continues to have a massive influence over what the ordinary person thinks about themselves.

"Dupré proposes that physiology does need a theory of normal and abnormal function, but that it does not need evolution to arrive at one"

Correct me if I misinterpreted this, but one example - obesity. Don't you need an evolutionary rationale on which to base an opinion of whether it reflects normal physiological function to respond to abundant food by indiscriminately storing it to the point of severe obesity, or if it rather indicates a pathological/abnormal state?

first off, Dupre's point is not that evolution is irrelevant here. But no, we understood that obesity was bad for our health well before there was any influence of evolutionary theory in medical practice. You can simply verify the physiologically negative effects of being obese and be done.